How old is my new dog? Which age is correct? 10 points!?

I adopted a dog at my local animal shelter, and I'm bringing him home in the morning. His paper that was attached to the cage, with his picture, ID #, etc. says that he is 4 years old. However; on the online database, it says that he is 7 years old. Could the online database just be a typo? What should I believe is the dogs actual age, until I take him to the vet?